Explanation:

The two options that are available for the administrator to make the shortcut available to all desktop pool users, while minimizing ongoing administrative effort, before updating the desktop pool golden image are:
Copy the shortcut to c:\users\Public\Desktop. This option will place the shortcut in the public desktop folder, which is shared by all users who log on to the same computer. The public desktop folder is normally a hidden folder, so the administrator needs to enable the option to show hidden files and folders in File Explorer1. This option does not require any additional software or configuration, but it will only work for the existing desktops in the pool. If new desktops are added or refreshed, the shortcut will not be copied automatically.
Configure a Shortcut with DEM (Dynamic Environment Manager). This option will use the DEM console to create a shortcut configuration that will apply the shortcut to the user's desktop during logon2. The administrator needs to install and configure DEM on the Horizon environment, and create a configuration share and a profile archive share for storing the DEM settings3. This option requires more initial setup, but it will work for any desktop in the pool, regardless of whether it is new or refreshed. It also allows more flexibility and control over the shortcut properties and conditions.
The other options are not valid or feasible because:
Copying the shortcut during user provisioning to a non-writeable App Volume will not work because App Volumes are used to deliver applications, not shortcuts. App Volumes are virtual disks that are attached to the virtual machines at runtime, and they contain application files, registry entries, and settings4. Copying a shortcut to an App Volume will not make it appear on the user's desktop.
Copying the shortcut to the Windows Default Domain Controller Policy will not work because this policy is used to configure settings for domain controllers, not desktops. The Default Domain Controller Policy is a Group Policy Object (GPO) that is linked to the Domain Controllers organizational unit (OU) in Active Directory, and it contains security settings that are applied to all domain controllers in the domain5. Copying a shortcut to this policy will not affect any desktops in the Horizon environment.
Configuring a Shortcut with Horizon View Client will not work because Horizon View Client is used to connect to remote desktops and applications, not to create shortcuts. Horizon View Client is a software application that runs on various devices and platforms, and it allows users to access their virtual desktops and applications through a secure connection6. Configuring a shortcut with Horizon View Client will not make it appear on the user's desktop.
References:
How to make a desktop shortcut available for all users in Windows 101
VMware Dynamic Environment Manager (DEM) 2306 - Carl Stalhood2
VMware Tech Zone Antivirus Considerations in a VMware Horizon Environment: exclusions for Horizon View, App Volumes, User Environment Manager, ThinApp3 App Volumes Overview Default Domain Controller Policy5 VMware Horizon Clients Documentation6

Explanation
Instant clones are a type of virtual machines that are created by cloning a running parent VM in memory, without requiring a full disk copy. This allows for faster provisioning and updating ofRDS hosts in a farm.
Instant clones can be patched in a rolling process with zero downtime by using the push-image operation, which replaces the existing instant clones with new ones that have the latest patches applied. The push-image operation can be performed on a per-farm basis or on multiple farms at once. The push-image operation preserves the user sessions and data on the existing instant clones until they are logged off or disconnected, and then deletes them. The new instant clones inherit the same settings and assignments as the old ones.
Therefore, to deploy a RDS farm that can be patched in a rolling process with zero downtime, the administrator should create an instant-clone RDS desktop farm. References: Instant Clones for RDSH in VMware Horizon 7.1 and [VMware Horizon 8.x Professional Course]

The disconnections of external sessions while internal sessions remain stable suggest an issue with the network infrastructure external to the Horizon environment, specifically with the load balancer placed in front of the Unified Access Gateway (UAG) appliances. Misconfigurations such as improper session persistence settings can lead to sessions being disconnected or improperly routed, causing the observed random disconnections.